This invention is directed to a cathode structure and the method of making the cathode.
The emissive material of a cathode must be accurately retained in position so that the emitted electron stream is in a known position. With shifting of the cathode, the source of the electron stream is shifted to produce beam inaccuracy. Maintaining the cathode in position has not been adequately accomplished because temperature cycling causes loosening of rigidly mounted mechanical structures. Furthermore, mechanical vibrations and testing operations tend to loosen a rigidly mounted cathode structure. A cathode such as shown in Schmitz U.S. Pat. No. 3,610,988 is subject to such loosening, as a result of heat cycling in testing and in use, due to radio frequency heating as well as cathode heater heating.
A structure which is capable of resisting loosening due to thermal cycling and mechanical stresses is required in order to maintain the cathode in place in devices where an accurately located electron beam is required.